Variable pitch mechanisms for propeller blades using a compound gearbox

ABSTRACT

Various mechanisms for adjusting pitches of propeller blades are described. For example, the pitch adjustment mechanism may include a propeller hub enclosing a geared mechanism that cooperates with a compound gearbox having first and second planetary stages to adjust pitches of propeller blades. Alternatively, the pitch adjustment mechanism may include a propeller hub enclosing a pitch adjustment assembly that utilizes tension cables and torsion springs, or rack-and-pinion structures, to adjust pitches of propeller blades. Using any of the various mechanisms, the pitches of propeller blades may be rotated at least 90 degrees, and up to and exceeding 360 degrees, in order to effect thrust reversals and/or adjust thrust profiles.

BACKGROUND

Aerial vehicles, including autonomous or automated aerial vehicles, mayutilize propellers and corresponding motors to generate lift and/orthrust. It may be desirable to vary pitches of one or more of thepropeller blades to alter a thrust profile or otherwise affect lift ormaneuverability of the aerial vehicles. However, existing mechanisms forvarying pitches of propeller blades suffer from limited range of motion,e.g., less than a 90 degree change of blade pitch. Accordingly, there isa need for propeller blade pitch adjustment mechanisms that can providea greater range of motion, e.g., greater than a 90 degree change ofblade pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical components or features.

FIG. 1 is a schematic diagram of a first propeller blade pitchadjustment apparatus, according to an implementation.

FIG. 2 is a schematic diagram of a propeller hub and a compound gearboxof the first propeller blade pitch adjustment apparatus, according to animplementation.

FIG. 3 is a schematic diagram of a first stage gearbox of the compoundgearbox of the first propeller blade pitch adjustment apparatus,according to an implementation.

FIG. 4 is a schematic diagram of a second stage gearbox of the compoundgearbox of the first propeller blade pitch adjustment apparatus,according to an implementation.

FIG. 5 is a schematic diagram of the compound gearbox of the firstpropeller blade pitch adjustment apparatus, according to animplementation.

FIG. 6A is a schematic diagram of a second propeller blade pitchadjustment apparatus, according to an implementation.

FIG. 6B is a schematic, partial cross-section diagram of the secondpropeller blade pitch adjustment apparatus, according to animplementation.

FIG. 6C is a schematic, partial cross-section diagram of pitchadjustment spools of the second propeller blade pitch adjustmentapparatus, according to an implementation.

FIG. 7A is a schematic diagram of a third propeller blade pitchadjustment apparatus, according to an implementation.

FIG. 7B is a schematic, partial cross-section diagram of pitchadjustment spools of the third propeller blade pitch adjustmentapparatus, according to an implementation.

FIG. 8 is a block diagram illustrating various components of an aerialvehicle control system, according to an implementation.

While implementations are described herein by way of example, thoseskilled in the art will recognize that the implementations are notlimited to the examples or drawings described. It should be understoodthat the drawings and detailed description thereto are not intended tolimit implementations to the particular form disclosed but, on thecontrary, the intention is to cover all modifications, equivalents andalternatives falling within the spirit and scope as defined by theappended claims. The headings used herein are for organizationalpurposes only and are not meant to be used to limit the scope of thedescription or the claims. As used throughout this application, the word“may” is used in a permissive sense (i.e., meaning having the potentialto), rather than the mandatory sense (i.e., meaning must). Similarly,the words “include,” “including,” and “includes” mean including, but notlimited to.

DETAILED DESCRIPTION

Various propeller blade pitch adjustment apparatuses are describedherein. Each of the example embodiments of pitch adjustment apparatusesallows a variation in pitch of a propeller blade of at least more than90 degrees and/or up to and exceeding 360 degrees, and some embodimentsallow potentially infinite variation in pitch of a propeller blade. Inaddition, for various embodiments described herein, the pitch of apropeller blade may be varied by actuation of a pitch adjustment shaftor a control shaft.

The pitch adjustment apparatuses as described herein may allow reversalof thrust, or inversion of a thrust profile, of a propeller andcorresponding motor without any reduction in propulsive efficiency. Forexample, the pitches of blades of a propeller may be rotatedapproximately 180 degrees using any of the pitch adjustment apparatusesdescribed herein, and the rotation of the motor may be reversed, therebyreversing the thrust, or inverting the thrust profile, of the propellerand corresponding motor without any reduction in propulsive efficiency.

Such reversal of thrust may be useful for aerial vehicles in order toslow down, stop, or move in a reverse direction, e.g., when the aerialvehicles are on the ground. In addition, reversal of thrust may beuseful for aerial vehicles to maintain stable flight in variousoperating conditions, e.g., in the case of one or more motor failures,or when operating in extreme environments, such as windy environments.Further, reversal of thrust may be useful for aerial vehicles thatutilize one or more propellers and corresponding motors for bothvertical takeoff and landing (VTOL) and also horizontal flight, e.g.,for aerial vehicles having propellers and corresponding motors that tiltbetween vertical and horizontal flight configurations. Many otherapplications of thrust reversal, or other desired changes in thrustprofiles, using the pitch adjustment apparatuses described herein arepossible. Moreover, although the present disclosure describes pitchadjustment apparatuses in the context of aerial vehicles, the pitchadjustment apparatuses described herein may be used in any othervehicles, machines, devices, or other systems that utilize propellers,fans, or other similar structures having blades, and that are rotated bymotors or other propulsion sources.

In some embodiments, the pitch adjustment apparatus may include apropeller hub and a compound gearbox. The propeller hub may be coupledto and rotated by a first end of a motor shaft that is rotated by arotor of a motor, and the motor shaft may be a hollow motor shaft. Thepropeller hub may include one or more propeller blade shafts, and eachof the propeller blade shafts may be connected to a propeller blade at afirst end that extends out of the propeller hub and may be connected toa blade gear, e.g., a bevel gear, at a second end within the propellerhub.

A pitch adjustment shaft may extend within and through the hollow motorshaft, and a pitch adjustment gear, e.g., a bevel gear, may be connectedto a first end of the pitch adjustment shaft within the propeller hub.The pitch adjustment gear may be in operative engagement with each ofthe blade gears associated with respective propeller blade shafts andpropeller blades. Accordingly, rotation of the pitch adjustment shaftand pitch adjustment gear may cause corresponding rotations of each ofthe blade gears, propeller blade shafts, and propeller blades to adjustpitches of the propeller blades.

The second end of the motor shaft and the second end of the pitchadjustment shaft may each be coupled to components within a compoundgearbox, e.g., gearbox. The gearbox may be configured to allow the motorshaft and the pitch adjustment shaft to rotate in a same direction at asame rotational speed such that during operation of the motor, thepropeller blades may rotate to generate thrust based on the rotation ofthe motor shaft, while also maintaining a desired pitch of the propellerblades during operation.

The compound gearbox, e.g., gearbox, may include a first stage gearbox,e.g., a first planetary stage, and a second stage gearbox, e.g., asecond planetary stage. The first stage gearbox may include a first sungear, a plurality of first planet gears carried by a first planetarygear carrier, and a ring gear. The second end of the motor shaft may beconnected to and rotate the first sun gear of the first stage gearbox.The plurality of first planet gears may be in operative engagement withthe first sun gear and carried by the first planetary gear carrier. Thefirst planetary gear carrier may be rotationally fixed, e.g., relativeto a stator of the motor, or another component coupled to the stator.The ring gear may be in operative engagement with the plurality of firstplanet gears and rotate around the plurality of first planet gears andthe first sun gear.

The second stage gearbox may include a second sun gear, a plurality ofsecond planet gears carried by a second planetary gear carrier, and thering gear. The plurality of second planet gears may be in operativeengagement with the ring gear, and rotation of the ring gear may causethe plurality of second planet gears to rotate on the second planetarygear carrier. The second planetary gear carrier may be selectivelyrotatable relative to a fixed position of the first planetary gearcarrier. The second sun gear may be in operative engagement with theplurality of second planet gears, and rotation of the plurality ofsecond planet gears may cause the second sun gear to rotate. The secondsun gear may be connected to and rotate the second end of the pitchadjustment shaft.

When the second planetary gear carrier is held in position relative tothe first planetary gear carrier, the motor shaft and the pitchadjustment shaft may rotate in a same direction at a same rotationalspeed, and the propeller blades may maintain a constant pitch. In orderto adjust the pitches of the propeller blades, the second planetary gearcarrier may be rotated relative to the first planetary gear carrier. Therotation of the second planetary gear carrier may cause rotation of thesecond planet gears, the second sun gear, the pitch adjustment shaft,and the pitch adjustment gear, and thereby may cause rotation of theblade gears, propeller blade shafts, and propeller blades to adjust thepitches of the propeller blades.

In other embodiments, the pitch adjustment apparatus may include apropeller hub that is coupled to and rotated by a motor shaft, and apropeller blade pitch adjustment assembly within the propeller hub. Themotor shaft may be hollow, and the propeller hub may enclose an interiorspace within which the propeller blade pitch adjustment assembly is atleast partially movably situated.

The propeller blade pitch adjustment assembly may include one or morepitch adjustment spools that are each coupled to a propeller blade thatextends outside the propeller hub. Each pitch adjustment spool mayrotate and thereby cause the propeller blade to rotate and adjust itspitch. The one or more pitch adjustment spools may be operativelyengaged with a control member that controls the rotation of the pitchadjustment spools. In addition, a control shaft may be rotatably coupledto the control member to adjust a position of the control member. Thecontrol shaft may extend through the hollow motor shaft.

In some embodiments, two or more pitch adjustment spools may berotatably connected to each other via a torsion spring, and each pitchadjustment spool may be connected to the control member via a tensioncable. The control member may be a plate, block, or other structure thatmoves within the propeller hub in a direction transverse to axes ofrotation of the pitch adjustment spools and propeller blades. Thecontrol shaft may be rotatably connected to the control member via abearing and also move within the propeller hub and the hollow motorshaft in a direction transverse to axes of rotation of the pitchadjustment spools and propeller blades. Movement of the control shaftand control member away from the pitch adjustment spools may pull thetension cables against a biasing force of the torsion spring and rotatethe pitch adjustment spools, thereby adjusting pitches of the propellerblades.

In further embodiments, two or more pitch adjustment spools may berotatably connected to each other, and each pitch adjustment spool mayinclude a gear, e.g., a pinion gear, on an outer surface. The controlmember may include racks, e.g., including gear teeth, on inner surfacesthat are operatively engaged with the gears of the pitch adjustmentspools, and the control member may move within the propeller hub in adirection transverse to axes of rotation of the pitch adjustment spoolsand propeller blades. The control shaft may be rotatably connected tothe control member via a bearing and also move within the propeller huband the hollow motor shaft in a direction transverse to axes of rotationof the pitch adjustment spools and propeller blades. Movement of thecontrol shaft and control member may rotate the pitch adjustment spoolsvia the racks and pinion gears, thereby adjusting pitches of thepropeller blades.

FIG. 1 is a schematic diagram of a first propeller blade pitchadjustment apparatus 100, according to an implementation. The apparatus100 may include a propeller hub 110 and a compound gearbox 120 that arearranged on either side of a motor 104. The motor 104 may be supportedon a motor arm 102 or other frame or body portion of an aerial vehicle.For example, the motor 104 may include a stator 106, and a rotor (notshown) that is coupled to and rotates a motor shaft 108. The motor shaft108 may be a hollow motor shaft that extends from opposing sides of themotor 104. In addition, a pitch adjustment shaft 122 may extend withinthe hollow motor shaft 108 between components within each of thepropeller hub 110 and the compound gearbox 120, as further describedwith respect to FIGS. 2-5.

At a first end, the motor shaft 108 may be coupled to the propeller hub110, as further described with respect to FIG. 2. Extending out from thepropeller hub 110 may be propeller blade shafts 112 and correspondingpropeller blades 114. Alternatively or in addition, the propeller bladeshafts 112 and propeller blades 114 may be integrally formed with eachother, or only the propeller blades 114 may extend from the propellerhub 110, with the propeller blade shafts 112 being substantiallyenclosed within the propeller hub 110. While FIG. 1 shows two propellerblade shafts 112-1, 112-2 and two corresponding propeller blades 114-1,114-2, any other number and arrangement of propeller blade shafts 112and propeller blades 114 may extend from the propeller hub 110.

When the motor shaft 108 is rotated by the rotor of the motor 104, thepropeller hub 110 may rotate together with the motor shaft 108, suchthat the propeller blade shafts 112 and propeller blades 114 alsorotate. Rotation of the propeller blades 114 may generate thrust,dependent on the shape and pitch of the propeller blades.

At a second end, the motor shaft 108 may be coupled to a componentwithin the compound gearbox 120, as further described with respect toFIGS. 3-5. As shown in FIG. 1, the compound gearbox 120 may include afirst planetary gear carrier 123 and a second planetary gear carrier124, each of which is further described with respect to FIGS. 3-5. Thefirst planetary gear carrier 123 may be coupled or fixed to the motorarm 102 and/or the stator 106 of the motor 104. Accordingly, the firstplanetary gear carrier 123 may be rotationally fixed relative to thestator 106 of the motor 104. The second planetary gear carrier 124 maybe rotatable relative to the first planetary gear carrier 123. Forexample, the second planetary gear carrier 124 may include gear teeth onan outer surface by which the second planetary gear carrier 124 may beselectively rotated, e.g., by an actuator.

FIG. 2 is a schematic diagram of a propeller hub 110 and a compoundgearbox 120 of the first propeller blade pitch adjustment apparatus 200,according to an implementation. The apparatus 200 shown in FIG. 2 issubstantially the same as the apparatus 100 shown in FIG. 1, but withsome elements removed and/or shown in outline for clarity ofdescription. The apparatus 200 may include a propeller hub 110 and acompound gearbox 120 that are arranged at opposite ends of a motor shaft108. The motor shaft 108 may be rotated by a rotor of a motor and may bea hollow motor shaft.

As described herein, a second end of the motor shaft 108 may be coupledto a component within the compound gearbox 120, as further describedwith respect to FIGS. 3-5. The compound gearbox 120 may include arotationally fixed first planetary gear carrier 123 and a selectivelyrotatable second planetary gear carrier 124, each of which is furtherdescribed with respect to FIGS. 3-5. In addition, a pitch adjustmentshaft 122 may extend within the hollow motor shaft 108, and a second endof the pitch adjustment shaft 122 may couple to a component within thecompound gearbox 120, as further described with respect to FIGS. 3-5.

A first end of the motor shaft 108 may be coupled to the propeller hub110. The propeller hub 110 may include a housing 210 that encloses aninterior space and one or more openings 212 through which propellerblade shafts 112 or propeller blades 114 may extend out from thepropeller hub 110. Portions of the propeller blade shafts 112, thepropeller blades 114, and the openings 212 may be circular orcylindrical in order to allow rotation of the propeller blade shafts 112or propeller blades 114 within the openings 212. In addition, each ofthe openings 212 may include one or more bearings or other similar,friction-reducing elements to facilitate rotation of the propeller bladeshafts 112 or propeller blades 114. While FIG. 2 shows two openings212-1, 212-2, any other number and arrangement of openings 212 may beprovided in the propeller hub 110 to accommodate the propeller bladeshafts 112 or propeller blades 114.

When the motor shaft 108 is rotated by the rotor of the motor, thepropeller hub 110, including the housing 210 and the openings 212, mayrotate together with the motor shaft 108, such that the propeller bladeshafts 112 and propeller blades 114 also rotate with rotation of themotor shaft 108. Rotation of the propeller blades 114 may generatethrust, dependent on the shape and pitch of the propeller blades.

Within the housing 210 of the propeller hub 110, each of the propellerblade shafts 112 may couple to a blade gear 217. The blade gears 217 maybe bevel gears, e.g., straight bevel gears or spiral bevel gears. Inaddition, each of the propeller blade shafts 112 and/or blade gears 217may include one or more bearings or other similar, friction-reducingelements to facilitate rotation of the blade gears 217 relative to thehousing 210. While FIG. 2 shows two blade gears 217-1, 217-2, any othernumber and arrangement of blade gears 217 associated with the propellerblade shafts 112 or propeller blades 114 may be provided within thepropeller hub 110.

Further, within the housing 210 of the propeller hub 110, the pitchadjustment shaft 122 may couple to a pitch adjustment gear 215 that isin operative engagement with each of the blade gears 217. The pitchadjustment gear 215 may be a bevel gear, e.g., a straight bevel gear ora spiral bevel gear. In addition, the pitch adjustment shaft 122 and/orthe pitch adjustment gear 215 may include one or more bearings or othersimilar, friction-reducing elements to facilitate rotation of the pitchadjustment gear 215 relative to the housing 210.

When the pitch adjustment shaft 122 is rotated via an input to acomponent of the compound gearbox, as further described herein withrespect to FIGS. 3-5, the pitch adjustment gear 215 may rotate togetherwith the pitch adjustment shaft 122. Rotation of the pitch adjustmentgear 215 may cause rotation of the blade gears 217 that are in operativeengagement with the pitch adjustment gear 215, and rotation of the bladegears 217 may cause corresponding rotation of the propeller blade shafts112 and propeller blades 114. Therefore, rotation of the pitchadjustment shaft 122 may cause rotation, i.e., changes in pitch, of eachof the propeller blades 114 that extend from the propeller hub 110.

For example, the operative engagement between the pitch adjustment gear215 and the blade gears 217 may ensure that each of the blade gears 217rotates in a same rotational direction in response to rotation of thepitch adjustment gear 215. Further, if all the blade gears 217 have thesame size and the same number of gear teeth, each of the blade gears 217may rotate a same degree of rotation, i.e., a same change in pitch ofthe propeller blades 114, in response to rotation of the pitchadjustment gear 215.

Furthermore, the housing 210 of the propeller hub 110 may be asubstantially closed system, such that lubricant may be maintainedwithin the propeller hub 110 to facilitate smooth engagement between thepitch adjustment gear 215 and the blade gears 217 and smooth rotation ofthe pitch adjustment shaft 122 and the propeller blade shafts 112, aswell as to prevent contamination and deterioration of the componentsand/or lubricant.

FIG. 3 is a schematic diagram of a first stage gearbox of the compoundgearbox 120 of the first propeller blade pitch adjustment apparatus 300,according to an implementation. The apparatus 300 shown in FIG. 3 issubstantially the same as the apparatuses 100, 200 shown in FIGS. 1 and2, but with some elements removed and/or shown in outline for clarity ofdescription. The apparatus 300 may include a compound gearbox 120 thatis arranged at one end of a motor shaft 108. The motor shaft 108 may berotated by a rotor of a motor and may be a hollow motor shaft.

As described herein, a first end of the motor shaft 108 may be coupledto a propeller hub 110, as further described with respect to FIG. 2. Thepropeller hub 110 may rotate with the motor shaft 108, and the propellerhub 110 may include components that allow adjustment of the pitches ofthe propeller blades that extend from the propeller hub 110.

The first stage gearbox, or first planetary stage, of the compoundgearbox 120 may include a first sun gear 315, a plurality of firstplanet gears 325 carried by a first planetary gear carrier 123, and aring gear 330. A second end of the motor shaft 108 may be coupled to thefirst sun gear 315, such that the first sun gear 315 may rotate togetherwith rotation of the motor shaft 108. The plurality of first planetgears 325 may be in operative engagement with the first sun gear 315.The plurality of first planet gears 325 may be carried on posts 323 orstems associated with the first planetary gear carrier 123. Although notshown in FIG. 3, the first planetary gear carrier 123 may be coupled toeach of the posts 323. In addition, the first planetary gear carrier 123may be rotationally fixed to the stator 106 of the motor 104, the motorarm 102, a frame or body portion of the aerial vehicle, or any othercomponent that does not rotate relative to the stator 106 of the motor104. Further, the ring gear 330 may be in operative engagement with eachof the plurality of first planet gears 325. In addition, each of themotor shaft 108, the first sun gear 315, the first planet gears 325,and/or the ring gear 330 may include one or more bearings or othersimilar, friction-reducing elements to facilitate their rotationrelative to the first planetary gear carrier 123 and/or the secondplanetary gear carrier 124. While FIG. 3 shows four first planet gears325-1, 325-2, 325-3, 325-4 on four posts 323-1, 323-2, 323-3, 323-4, anyother number and arrangement of first planet gears 325 and posts 323 maybe provided within the first stage gearbox.

When the motor shaft 108 is rotated by the rotor of the motor, the firstsun gear 315 may rotate together with the motor shaft 108. Rotation ofthe first sun gear 315 may cause rotation of each of the plurality offirst planet gears 325 on the rotationally fixed first planetary gearcarrier 123, and rotation of the plurality of first planet gears 325 maycause rotation of the ring gear 330. The ring gear 330 may rotate in anopposite rotational direction from the direction of rotation of thefirst sun gear 315, and the ring gear 330 may rotate at a differentrotational speed from the speed of rotation of the first sun gear 315.

FIG. 4 is a schematic diagram of a second stage gearbox of the compoundgearbox 120 of the first propeller blade pitch adjustment apparatus 400,according to an implementation. The apparatus 400 shown in FIG. 4 issubstantially the same as the apparatuses 100, 200, 300 shown in FIGS.1-3, but with some elements removed and/or shown in outline for clarityof description. The apparatus 400 may include a compound gearbox 120that is arranged at one end of a motor shaft 108. The motor shaft 108may be rotated by a rotor of a motor and may be a hollow motor shaft.

The second stage gearbox, or second planetary stage, of the compoundgearbox 120 may include a second sun gear 415, a plurality of secondplanet gears 425 carried by a second planetary gear carrier 124, and thering gear 330 that is shared between the first stage gearbox and thesecond stage gearbox. A second end of the pitch adjustment shaft 122 mayextend through both the hollow motor shaft 108 and the first sun gear315 and may be coupled to the second sun gear 415, such that the pitchadjustment shaft 122 rotates together with rotation of the second sungear 415. The plurality of second planet gears 425 may be in operativeengagement with the second sun gear 415. The plurality of second planetgears 425 may be carried on posts 423 or stems associated with thesecond planetary gear carrier 124. The second planetary gear carrier 124may be coupled to each of the posts 423. In addition, the secondplanetary gear carrier 124 may be selectively rotatable relative to thestator 106 of the motor 104, the motor arm 102, a frame or body portionof the aerial vehicle, or any other component that is fixed relative tothe stator 106 of the motor 104. Further, the ring gear 330 may be inoperative engagement with each of the plurality of second planet gears425. In addition, each of the pitch adjustment shaft 122, the second sungear 415, the second planet gears 425, and/or the ring gear 330 mayinclude one or more bearings or other similar, friction-reducingelements to facilitate their rotation relative to the first planetarygear carrier 123 and/or the second planetary gear carrier 124. WhileFIG. 4 shows four second planet gears 425-1, 425-2, 425-3, 425-4 on fourposts 423-1, 423-2, 423-3, 423-4, any other number and arrangement ofsecond planet gears 425 and posts 423 may be provided within the secondstage gearbox.

When, as described herein, the ring gear 330 is rotated as a result ofrotation of the motor shaft 108 by the rotor of the motor, the secondplanet gears 425 may rotate on the selectively rotatable secondplanetary gear carrier 124. Rotation of the second planet gears 425 maycause rotation of the second sun gear 415, and rotation of the secondsun gear 415 may cause rotation of the pitch adjustment shaft 122. Ifthe first sun gear 315 and the second sun gear 415 have the same sizeand the same number of gear teeth, if all the first planet gears 325 andthe second planet gears 425 have the same size and the same number ofgear teeth, and if the second planetary gear carrier 124 is held inposition relative to the first planetary gear carrier 123, the motorshaft 108 and the pitch adjustment shaft 122 may rotate in the samerotational direction at the same rotational speed. As a result, duringoperation of the motor, the propeller blades may rotate to generatethrust based on the rotation of the motor shaft, while also maintaininga desired pitch of the propeller blades during operation.

In order to adjust pitches of the propeller blades, the second planetarygear carrier 124 may be selectively rotated relative to the firstplanetary gear carrier 123. For example, as shown in FIGS. 1-4, thesecond planetary gear carrier 124 may include gear teeth on an outersurface thereof, and an actuator 127 having corresponding gear teeth maybe in operative engagement with the gear teeth of the second planetarygear carrier 124 to adjust the rotational position of the secondplanetary gear carrier 124. The actuator 127 may be a servo actuator, ageared actuator, a rotary actuator, a rack and pinion actuator, a screwactuator, and/or any other type of actuator. Alternatively or inaddition, any other method of actuating the second planetary gearcarrier 124 may be used instead of the gear teeth on the outer surfacethereof. For example, a portion of the second planetary gear carrier 124may be directly connected to an actuator 127, e.g., a servo actuator, amotor, or any other type of actuator, to adjust the rotational positionof the second planetary gear carrier 124. Other types of actuationmechanisms may also be used, such as pulley-type mechanisms to adjustthe rotational position of the second planetary gear carrier 124.

As an illustration, if the motor shaft 108 is not rotated by the rotorof the motor, and the first stage gearbox and the second stage gearboxof the compound gearbox 120 are not being actuated by the motor, themotor shaft 108, the first sun gear 315, the first planet gears 325, thering gear 330, the second planet gears 425, the second sun gear 415, andthe pitch adjustment shaft 122 may be stationary. If the secondplanetary gear carrier 124 is then rotated relative to the firstplanetary gear carrier 123 to adjust the pitches of the propeller blades112 via the propeller hub 110, the rotation of the second planetary gearcarrier 124 may cause rotation of the second planet gears 425 such thatthe second planet gears 425 rotate within the ring gear 330. The ringgear 330 may be held stationary by the stationary motor shaft 108 andthe first stage gearbox. The rotation of the second planet gears 425within the ring gear 330 may cause the second sun gear 415 to rotate,and thereby may cause rotation of the pitch adjustment shaft 122. Then,as described herein, the rotation of the pitch adjustment shaft 122 maycause adjustment of the pitches of the propeller blades 112 via thepropeller hub 110. While the adjustment of pitches of the propellerblades 112 is described herein in the context of a stationary motorshaft 108 for ease of illustration, the second planetary gear carrier124 may also be rotated relative to the first planetary gear carrier 123during rotation of the motor shaft 108, e.g., during operation of themotor, to adjust the pitches of the propeller blades 112.

Furthermore, the compound gearbox 120 may be a substantially closedsystem, such that lubricant may be maintained within the compoundgearbox 120 to facilitate smooth engagement between the first sun gear315, the first planet gears 325, the ring gear 330, the second planetgears 425, and the second sun gear 415 and smooth rotation of the motorshaft 108 and the pitch adjustment shaft 122, as well as to preventcontamination and deterioration of the components and/or lubricant.

FIG. 5 is a schematic diagram of the compound gearbox 120 of the firstpropeller blade pitch adjustment apparatus 500, according to animplementation. The apparatus 500 shown in FIG. 5 is substantially thesame as the apparatuses 100, 200, 300, 400 shown in FIGS. 1-4, but withsome elements removed and/or shown in outline for clarity ofdescription. The apparatus 500 may include a compound gearbox 120 thatis arranged at one end of a motor shaft 108. The motor shaft 108 may berotated by a rotor of a motor and may be a hollow motor shaft.

FIG. 5 shows an underside view of the compound gearbox 120 with thefirst planetary gear carrier 123 and the second planetary gear carrier124 removed for clarity. Thus, FIG. 5 shows the motor shaft 108, thefirst sun gear 315, the first planet gears 325, the ring gear 330, thesecond planet gears 425, the second sun gear 415, and the pitchadjustment shaft 122, as described herein with respect to FIGS. 1-4.Further, while FIGS. 3-5 show the first stage gearbox and the secondstage gearbox having the same number of planet gears, e.g., four firstplanet gears and four second planet gears, any other number andarrangement of first or second planet gears 325, 425 may be providedwithin the first or second stage gearboxes, e.g., four first planetgears and three second planet gears.

Each of the components of the propeller hub 110 and the compound gearbox120 may be made from any suitable materials, such as metal, plastics,carbon fiber, other materials, or combinations thereof, for example. Inaddition, the various gears may be coupled to the various shafts usingany suitable connection methods, such as keyed connections, frictionallyengaged connections, screw connections, set screws, adhesives, otherconnections, or combinations thereof. Alternatively or in addition, oneor more of the various gears may be integrally formed with theirrespective shafts. Further, while FIGS. 1 and 2 show the propeller hub110 having a substantially rectangular prism shape, any other shape orconfiguration of the propeller hub 110 is possible, e.g., circularprism, elliptical prism, hexagonal prism, octagonal prism, or otherpolygonal prism.

The first propeller blade pitch adjustment apparatuses 100, 200, 300,400, 500, including the propeller hub 110 and the compound gearbox 120,as described herein with respect to FIGS. 1-5, may allow a variation inpitches of propeller blades of at least more than 90 degrees, and mayallow potentially infinite variation in pitches of propeller blades.Accordingly, thrust reversal of a propeller and corresponding motor maybe accomplished without any reduction in propulsive efficiency using thefirst propeller blade pitch adjustment apparatuses to adjust the pitchesof propeller blades by approximately 180 degrees and reversing arotation of the motor. Moreover, various other changes to the thrustprofile of a propeller and corresponding motor may be accomplished usingthe first propeller blade pitch adjustment apparatuses to adjust thepitches of propeller blades as desired.

In an alternative embodiment to FIGS. 1-5, the compound gearbox 120 maybe situated between the motor 104 and the propeller hub 110, with thefirst stage gearbox of the compound gearbox 120 adjacent the motor 104and the second stage gearbox of the compound gearbox 120 adjacent thepropeller hub 110. Accordingly, the first planetary gear carrier may berotationally fixed relative to and situated adjacent a stator of themotor 104, and the second planetary gear carrier may be selectivelyrotatable and situated adjacent the propeller hub 110.

In this alternative embodiment, the pitch adjustment shaft 122 mayinstead be a hollow pitch adjustment shaft, and the motor shaft 108 mayextend within and through the hollow pitch adjustment shaft. The motorshaft may be coupled to and extend through the first sun gear 315 of thefirst stage gearbox, then extend through the compound gearbox 120 withinthe hollow pitch adjustment shaft and couple to a portion of thepropeller hub 110, e.g., a portion of the propeller hub 110 distal fromthe motor 104. The hollow pitch adjustment shaft may be coupled to thesecond sun gear 415 at a first end and coupled to a pitch adjustmentgear within the propeller hub 110 at a second end.

The propeller hub 110 in this alternative embodiment may besubstantially similar to that described herein with respect to FIGS. 1and 2, except that the pitch adjustment shaft may be hollow, and themotor shaft may extend through the hollow pitch adjustment shaft and thepitch adjustment gear and couple to a portion of the propeller hub 110,e.g., a portion of the propeller hub 110 distal from the motor 104, inorder to rotate the propeller hub 110 together with rotation of themotor shaft.

The compound gearbox 120 in this alternative embodiment may also besubstantially similar to that described herein with respect to FIGS.2-5, except that the pitch adjustment shaft may be hollow, and the motorshaft may couple to and extend through the first sun gear 315 and thenextend through the hollow pitch adjustment shaft and the second sun gear415 en route to the propeller hub 110, as described herein.

FIG. 6A is a schematic diagram of a second propeller blade pitchadjustment apparatus 600, and FIG. 6B is a schematic, partialcross-section diagram of the second propeller blade pitch adjustmentapparatus 600, according to an implementation. The apparatus 600 mayinclude a propeller hub 110 coupled to a motor shaft 108 that is rotatedby a rotor of a motor. The motor shaft 108 may be a hollow motor shaftthat extends from the motor. In addition, a control shaft 610 may extendwithin the hollow motor shaft 108 between components within thepropeller hub 110 and a side of the motor opposite the propeller hub110.

The propeller hub 110 may be coupled to and rotate together withrotation of the motor shaft 108. In addition, the propeller hub 110 maybe formed integrally with the motor shaft 108. The propeller hub 110 mayalso include one or more openings 624 through which propeller bladeshafts 112 or propeller blades may extend from the propeller hub 110.The openings 624 may be circular, cylindrical, or otherwise shaped toallow changes in pitches of the propeller blades connected to thepropeller blade shafts 112. In addition, the openings 624 may includebearings or other similar, friction-reducing elements to facilitaterotation of the propeller blade shafts 112 or propeller blades. WhileFIGS. 6A and 6B show two openings 624-1, 624-2 and two propeller bladeshafts 112-1, 112-2 or propeller blades, any other number andarrangement of openings 624 and propeller blade shafts 112 and propellerblades may be provided that extend from the propeller hub 110.

A propeller blade pitch adjustment assembly may be situated within thepropeller hub 110. The propeller blade pitch adjustment assembly mayinclude a control shaft 610, a control member 615, one or more pitchadjustment spools 620 coupled to the propeller blade shafts 112 orpropeller blades, one or more tension cables 622, and one or moretorsion springs 625. The control shaft 610 may extend within and throughthe hollow motor shaft 108 and be rotatably coupled to the controlmember 615. For example, the control shaft 610 may include bearings orother similar, friction-reducing elements to facilitate rotation of thecontrol shaft 610 relative to the control member 615. On a side of themotor opposite the propeller hub 110, the control shaft 610 may extendpast the motor and be actuated by an actuator, e.g., a servo actuator, ageared actuator, a motor, a rotary actuator, a rack and pinion actuator,a screw actuator, a linear actuator, and/or any other type of actuator.

Alternatively, the control shaft 610 may be coupled directly to thecontrol member 615 and rotate together with the control member 615,propeller hub 110, and motor shaft 108. On a side of the motor oppositethe propeller hub 110, the end of the control shaft 610 may extend pastthe motor and be rotatably coupled to an actuator. For example, the endof the control shaft 610 may include bearings or other similar,friction-reducing elements to facilitate rotation of the control shaft610 relative to a connection to the actuator, such that the actuatorneed not rotate together with the control shaft 610 and motor shaft 108.

The control member 615 may comprise a plate, block, or other structurethat may move within the propeller hub 110. For example, the controlmember 615 may be pushed or pulled by the control shaft 610 in adirection parallel to an axial length of the control shaft 610. Inaddition, the direction of motion of the control member 615 may besubstantially transverse to axes of rotation of the pitch adjustmentspools 620, propeller blade shafts 112 and propeller blades. The controlmember 615 may include protrusions 616 that extend into grooves 617 ofthe propeller hub 110 to facilitate the movement of the control member615 upon actuation by the control shaft 610. Alternatively or inaddition, the control member 615 may include grooves into whichprotrusions of the propeller hub 110 extend to facilitate movement ofthe control member 615. Further, any other structures or formationsalong portions of the mating surfaces of the control member 615 andpropeller hub 110 may be used to facilitate movement of the controlmember 615, such as guides, tracks, rods, linear bearings, other similarfriction-reducing elements, or any other cooperating shapes orstructures between the control member 615 and the propeller hub 110. Insome embodiments, the control member 615 may be sized to substantiallyfill the cross-sectional shape of the propeller hub 110. While FIGS. 6Aand 6B show two protrusions 616-1, 616-2 and two grooves 617-1, 617-2 onthe control member 615 and propeller hub 110, respectively, any othernumber and arrangement of protrusions, grooves, or other structures orformations may be provided to facilitate movement of the control member615 within the propeller hub 110.

The pitch adjustment spools 620 may be coupled to the propeller bladeshafts 112 and propeller blades, and the pitch adjustment spools 620 maybe rotatably coupled to each other. FIG. 6C is a schematic, partialcross-section diagram of pitch adjustment spools 620 of the secondpropeller blade pitch adjustment apparatus 600, according to animplementation. For example, as shown in FIG. 6C, the pitch adjustmentspools 620 may have portions that overlap with each other, such that thepitch adjustment spools 620 may rotate about a same axis of rotation.The interfaces between the pitch adjustment spools 620 may includebearings or other similar, friction-reducing elements to facilitaterotation of the pitch adjustment spools 620 relative to each other. Inaddition, the pitch adjustment spools 620 may be connected to each othervia a torsion spring 625 that may bias the pitch adjustment spools 620to particular rotational positions relative to each other. The torsionspring 625 may bias the pitch adjustment spools 620 in oppositerotational directions from each other. The torsion spring 625 may beattached to the pitch adjustment spools 620 using screws, rivets,clamps, any other types of fasteners, welds, adhesives, or any otherattachment methods.

The pitch adjustment spools 620 may be coupled to the control member 615via tension cables 622. For example, the tension cables 622 may be steelwires or any other connecting wire or cable. The tension cables 622 maybe attached to portions of the pitch adjustment spools 620 at theirfirst ends, and attached to portions of the control member 615 at theirsecond ends. The tension cables 622 may be attached at their first andsecond ends using screws, rivets, clamps, any other types of fasteners,welds, adhesives, or any other attachment methods. The attachment pointsof the tension cables 622 to the pitch adjustment spools 620 may beconfigured such that movement of the control member 615, e.g., inresponse to pulling by the control shaft 610, may cause rotation of thepitch adjustment spools 620 in opposite rotational directions againstthe biasing force of the torsion spring 625. The tension cables 622 mayalso run along grooves or channels provided on surfaces of the pitchadjustment spools 620.

When the motor shaft 108 is rotated by the rotor of the motor, thepropeller hub 110 may rotate together with the motor shaft 108. Rotationof the propeller hub 110 may cause rotation of the control member 615via the mating surfaces or connections, e.g., protrusions 616 andgrooves 617, between the control member 615 and the propeller hub 110.Rotation of the propeller hub 110 may also cause rotation of the pitchadjustment spools 620, propeller blade shafts 112 and propeller bladesvia the openings 624 through which the propeller blade shafts 112 orpropeller blades extend from the propeller hub 110. As a result, thepropeller hub 110, the control member 615, the pitch adjustment spools620, the tension cables 622, the torsion spring 625, the propeller bladeshafts 112 and the propeller blades may rotate together with the motorshaft 108. In contrast, the control shaft 610, via the rotatableconnection to the control member 615 in one embodiment, may notnecessarily rotate together with the propeller hub 110 and the remainderof the propeller blade pitch adjustment assembly. In an alternativeembodiment in which the control shaft 610 is directly coupled to thecontrol member 615, the control shaft 610 may rotate together with thepropeller hub 110, the motor shaft 108, and the remainder of thepropeller blade pitch adjustment assembly, and the control shaft 610 mayinclude a rotatable connection to the actuator on an opposite side ofthe motor, such that the actuator need not rotate together with thecontrol shaft 610, the motor shaft 108, the propeller hub 110, and theremainder of the propeller blade pitch adjustment assembly.

When adjustments to pitches of the propeller blades are desired, thecontrol shaft 610 may be moved relative to the propeller hub 110, e.g.,pulled in a direction away from and transverse to axes of rotation ofthe pitch adjustment spools 620, propeller blade shafts 112, andpropeller blades. The movement of the control shaft 610 may also movethe control member 615 away from and transverse to axes of rotation ofthe pitch adjustment spools 620, propeller blade shafts 112, andpropeller blades. The movement of the control member 615 may pull thetension cables 622, thereby rotating the pitch adjustment spools 620against the biasing force of the torsion spring 625. The pitchadjustment spools 620 may rotate in opposite rotational directions inresponse to pulling by the tension cables 622, such that the propellerblade shafts 112 and propeller blades may rotate to adjust the pitchesof the propeller blades by substantially the same degree of rotation.

While FIGS. 6A and 6B show two pitch adjustment spools 620-1, 620-2, twotension cables 622-1, 622-2, and one torsion spring 625 thatinterconnects the two pitch adjustment spools 620-1, 620-2, any othernumber and arrangement of pitch adjustment spools 620, tension cables622, and torsion springs 625 may be provided in the second propellerblade pitch adjustment apparatus 600. For example, if the secondpropeller blade pitch adjustment apparatus 600 includes three or morepitch adjustment spools 620, the pitch adjustment spools 620 may each berotatably coupled to a central member, e.g., that is fixed relative tothe propeller hub 110, via a respective torsion spring 625, and thepitch adjustment spools 620 may each be coupled to the control member615 by a respective tension cable 622. In this manner, the pitches ofthree or more propeller blades may be substantially simultaneouslyadjusted using the second propeller blade pitch adjustment apparatus600.

Furthermore, the propeller hub 110 may be a substantially closed system,such that lubricant may be maintained within the propeller hub 110 tofacilitate smooth engagement between the control member 615 and thepropeller hub 110, smooth operation of the control shaft 610 and thepitch adjustment spools 620, and smooth rotation of the propeller bladeshafts 112 and propeller blades, as well as to prevent contamination anddeterioration of the components and/or lubricant.

Each of the components of the second propeller blade pitch adjustmentapparatus 600, including the motor shaft 108, propeller hub 110, controlshaft 610, control member 615, pitch adjustment spools 620, tensioncables 622, torsion spring 625, and/or propeller blade shafts 112 andpropeller blades, may be made from any suitable materials, such asmetal, plastics, carbon fiber, other materials, or combinations thereof,for example. In addition, the pitch adjustment spools may be coupled tothe propeller blade shafts or propeller blades using any suitableconnection methods, such as keyed connections, frictionally engagedconnections, screw connections, set screws, adhesives, otherconnections, or combinations thereof. Alternatively or in addition, oneor more of the pitch adjustment spools may be integrally formed withtheir respective propeller blade shafts or propeller blades. Further,while FIGS. 6A and 6B show the second propeller blade adjustmentapparatus 600 having a substantially rectangular prism shape, any othershape or configuration of the apparatus 600 is possible, e.g., circularprism, elliptical prism, hexagonal prism, octagonal prism, or otherpolygonal prism.

The second propeller blade pitch adjustment apparatus 600, including thepropeller hub 110 and propeller blade pitch adjustment assembly enclosedtherein, as described herein with respect to FIGS. 6A-6C, may allow avariation in pitches of propeller blades of at least more than 90degrees, and may allow a variation in pitches of propeller blades of upto 360 degrees or more, e.g., if the tension cables are wound around thepitch adjustment spools one or more times and with sufficient availabletravel of the control shaft and control member. Accordingly, thrustreversal of a propeller and corresponding motor may be accomplishedwithout any reduction in propulsive efficiency using the secondpropeller blade pitch adjustment apparatus to adjust the pitches ofpropeller blades by approximately 180 degrees and reversing a rotationof the motor. Moreover, various other changes to the thrust profile of apropeller and corresponding motor may be accomplished using the secondpropeller blade pitch adjustment apparatus to adjust the pitches ofpropeller blades as desired.

FIG. 7A is a schematic diagram of a third propeller blade pitchadjustment apparatus 700, according to an implementation. The apparatus700 may include a propeller hub 110 coupled to a motor shaft 108 that isrotated by a rotor of a motor. The motor shaft 108 may be a hollow motorshaft that extends from the motor. In addition, a control shaft 710 mayextend within the hollow motor shaft 108 between components within thepropeller hub 110 and a side of the motor opposite the propeller hub110.

The propeller hub 110 may be coupled to and rotate together withrotation of the motor shaft 108. In addition, the propeller hub 110 maybe formed integrally with the motor shaft 108. The propeller hub 110 mayalso include one or more openings 724 through which propeller bladeshafts 112 or propeller blades may extend from the propeller hub 110.The openings 724 may be circular, cylindrical, or otherwise shaped toallow changes in pitches of the propeller blades connected to thepropeller blade shafts 112. In addition, the openings 724 may includebearings or other similar, friction-reducing elements to facilitaterotation of the propeller blade shafts 112 or propeller blades. WhileFIG. 7A shows two openings 724-1 (hidden from view), 724-2 and twopropeller blade shafts 112-1, 112-2 or propeller blades, any othernumber and arrangement of openings 724 and propeller blade shafts 112and propeller blades may be provided that extend from the propeller hub110.

A propeller blade pitch adjustment assembly may be situated within thepropeller hub 110. The propeller blade pitch adjustment assembly mayinclude a control shaft 710, a control member 715, and one or more pitchadjustment spools 720 coupled to the propeller blade shafts 112 orpropeller blades. The control shaft 710 may extend within and throughthe hollow motor shaft 108 and be rotatably coupled to the controlmember 715. For example, the control shaft 710 may include bearings orother similar, friction-reducing elements to facilitate rotation of thecontrol shaft 710 relative to the control member 715. On a side of themotor opposite the propeller hub 110, the control shaft 710 may extendpast the motor and be actuated by an actuator, e.g., a servo actuator, ageared actuator, a motor, a rotary actuator, a rack and pinion actuator,a screw actuator, a linear actuator, and/or any other type of actuator.

Alternatively, the control shaft 710 may be coupled directly to thecontrol member 715 and rotate together with the control member 715,propeller hub 110, and motor shaft 108. On a side of the motor oppositethe propeller hub 110, the end of the control shaft 710 may extend pastthe motor and be rotatably coupled to an actuator. For example, the endof the control shaft 710 may include bearings or other similar,friction-reducing elements to facilitate rotation of the control shaft710 relative to a connection to the actuator, such that the actuatorneed not rotate together with the control shaft 710 and motor shaft 108.

The control member 715 may comprise a plate, block or other structurethat may move within the propeller hub 110. For example, the controlmember 715 may be pushed or pulled by the control shaft 710 in adirection parallel to an axial length of the control shaft 710. Inaddition, the direction of motion of the control member 715 may besubstantially transverse to axes of rotation of the pitch adjustmentspools 720, propeller blade shafts 112 and propeller blades. The controlmember 715 may include racks 717, e.g., including gear teeth, that areoperatively engaged with gear teeth on the pitch adjustment spools 720.For example, each rack 717 may be configured to operatively engage withgear teeth of a respective pitch adjustment spool 720. The controlmember 715 may also include slots 719 that allow movement of the controlmember 715 without interfering with the propeller blade shafts 112 andpropeller blades that extend from the propeller hub 110. In alternativeembodiments, the slots 719 may comprise openings at portions of thecontrol member 715 that allow movement of the control member 715 withoutinterfering with the propeller blade shafts 112 and propeller blades.Similar to the apparatus 600 of FIGS. 6A-6C, the control member 715 mayinclude protrusions and/or grooves that cooperate with grooves and/orprotrusions of the propeller hub 110 to facilitate the movement of thecontrol member 715 upon actuation by the control shaft 710. Further, anyother structures or formations along portions of the mating surfaces ofthe control member 715 and propeller hub 110 may be used to facilitatemovement of the control member 715, such as guides, tracks, rods, linearbearings, other similar friction-reducing elements, or any othercooperating shapes or structures between the control member 715 and thepropeller hub 110. In some embodiments, the control member 715 may besized to substantially fill the cross-sectional shape of the propellerhub 110.

The pitch adjustment spools 720 may be coupled to the propeller bladeshafts 112 and propeller blades, and the pitch adjustment spools 720 maybe rotatably coupled to each other. FIG. 7B is a schematic, partialcross-section diagram of pitch adjustment spools 720 of the thirdpropeller blade pitch adjustment apparatus 700, according to animplementation. For example, as shown in FIG. 7B, the pitch adjustmentspools 720 may have portions that overlap with each other, such that thepitch adjustment spools 720 rotate about a same axis of rotation. Theinterfaces between the pitch adjustment spools 720 may include bearingsor other similar, friction-reducing elements to facilitate rotation ofthe pitch adjustment spools 720 relative to each other.

The pitch adjustment spools 720 may also include gears, e.g., gear teethon an outer surface of each of the pitch adjustment spools 720. The gearteeth of the pitch adjustment spools 720 may operatively engage with thegear teeth of respective racks 717 on the inner surfaces of the controlmember 715. As shown in FIG. 7A, each rack 717 of the control member 715may be operatively engaged with gear teeth of a respective pitchadjustment spool 720 to cause rotation of the pitch adjustment spools720 in opposite rotational directions, such that the pitches ofpropeller blades coupled to the pitch adjustment spools 720 viapropeller blade shafts 112 are rotated by a same degree of rotation.

When the motor shaft 108 is rotated by the rotor of the motor, thepropeller hub 110 may rotate together with the motor shaft 108. Rotationof the propeller hub 110 may cause rotation of the control member 715via the mating surfaces or connections, e.g., protrusions and grooves,between the control member 715 and the propeller hub 110. Rotation ofthe propeller hub 110 may also cause rotation of the pitch adjustmentspools 720, propeller blade shafts 112 and propeller blades via theopenings 724 through which the propeller blade shafts 112 or propellerblades extend from the propeller hub 110. As a result, the propeller hub110, the control member 715, the pitch adjustment spools 720, thepropeller blade shafts 112 and the propeller blades may rotate togetherwith the motor shaft 108. In contrast, the control shaft 710, via therotatable connection to the control member 715 in one embodiment, maynot necessarily rotate together with the propeller hub 110 and theremainder of the propeller blade pitch adjustment assembly. In analternative embodiment in which the control shaft 710 is directlycoupled to the control member 715, the control shaft 710 may rotatetogether with the propeller hub 110, the motor shaft 108, and theremainder of the propeller blade pitch adjustment assembly, and thecontrol shaft 710 may include a rotatable connection to the actuator onan opposite side of the motor, such that the actuator need not rotatetogether with the control shaft 710, the motor shaft 108, the propellerhub 110, and the remainder of the propeller blade pitch adjustmentassembly.

When adjustments to pitches of the propeller blades are desired, thecontrol shaft 710 may be moved relative to the propeller hub 110, e.g.,pushed in a direction toward or pulled in a direction away from andtransverse to axes of rotation of the pitch adjustment spools 720 andpropeller blade shafts 112 and propeller blades. The movement of thecontrol shaft 710 may also move the control member 715 in acorresponding direction toward or away from and transverse to axes ofrotation of the pitch adjustment spools 720 and propeller blade shafts112 and propeller blades. The movement of the control member 715 maycause the pitch adjustment spools 720 to rotate due to the operativeengagement between the gear teeth on the pitch adjustment spools 720 andthe gear teeth on the racks 717 of the control member 715. The pitchadjustment spools 720 may rotate in opposite rotational directions inresponse to pushing or pulling by the control member 715, such that thepropeller blade shafts 112 and propeller blades may rotate to adjust thepitches of the propeller blades by substantially the same degree ofrotation.

While FIG. 7A shows two pitch adjustment spools 720-1, 720-2, two racks717-1, 717-2, and two slots 719-1, 719-2, any other number andarrangement of pitch adjustment spools 720, racks 717, and slots 719 maybe provided in the third propeller blade pitch adjustment apparatus 700.For example, if the third propeller blade pitch adjustment apparatus 700includes three or more pitch adjustment spools 720, the pitch adjustmentspools 720 may each be rotatably coupled to a central member, e.g., thatis fixed relative to the propeller hub 110, and gear teeth of each ofthe pitch adjustment spools 720 may be coupled to a respective rack 717of the control member 715. In this manner, the pitches of three or morepropeller blades that extend from the propeller hub 110 via respectiveslots 719 may be substantially simultaneously adjusted using the thirdpropeller blade pitch adjustment apparatus 700.

Furthermore, the propeller hub 110 may be a substantially closed system,such that lubricant may be maintained within the propeller hub 110 tofacilitate smooth engagement between the control member 715 and thepropeller hub 110, smooth engagement between the gear teeth of thecontrol member 715 and the gear teeth of the pitch adjustment spools720, smooth operation of the control shaft 710 and the pitch adjustmentspools 720, and smooth rotation of the propeller blade shafts 112 andpropeller blades, as well as to prevent contamination and deteriorationof the components and/or lubricant.

Each of the components of the third propeller blade pitch adjustmentapparatus 700, including the motor shaft 108, propeller hub 110, controlshaft 710, control member 715, racks 717, pitch adjustment spools 720,and/or propeller blade shafts 112 and propeller blades, may be made fromany suitable materials, such as metal, plastics, carbon fiber, othermaterials, or combinations thereof, for example. In addition, the pitchadjustment spools may be coupled to the propeller blade shafts using anysuitable connection methods, such as keyed connections, frictionallyengaged connections, screw connections, set screws, adhesives, otherconnections, or combinations thereof. Alternatively or in addition, oneor more of the pitch adjustment spools may be integrally formed withtheir respective propeller blade shafts. Further, while FIG. 7A showsthe third propeller blade adjustment apparatus 700 having asubstantially rectangular prism shape, any other shape or configurationof the apparatus 700 is possible, e.g., circular prism, ellipticalprism, hexagonal prism, octagonal prism, or other polygonal prism.

The third propeller blade pitch adjustment apparatus 700, including thepropeller hub 110 and propeller blade pitch adjustment assembly enclosedtherein, as described herein with respect to FIGS. 7A-7B, may allow avariation in pitches of propeller blades of at least more than 90degrees, and may allow a variation in pitches of propeller blades of upto 360 degrees or more, e.g., with sufficient available travel of thecontrol shaft and control member. Accordingly, thrust reversal of apropeller and corresponding motor may be accomplished without anyreduction in propulsive efficiency using the third propeller blade pitchadjustment apparatus to adjust the pitches of propeller blades byapproximately 180 degrees and reversing a rotation of the motor.Moreover, various other changes to the thrust profile of a propeller andcorresponding motor may be accomplished using the third propeller bladepitch adjustment apparatus to adjust the pitches of propeller blades asdesired.

FIG. 8 is a block diagram illustrating various components of an exampleaerial vehicle control system 800 of an example aerial vehicle which mayutilize one or more of the propeller blade pitch adjustment apparatusesdescribed herein, according to an implementation. In various examples,the block diagram may be illustrative of one or more aspects of theaerial vehicle control system 800 that may be used to implement thevarious systems and processes discussed above. In the illustratedimplementation, the aerial vehicle control system 800 includes one ormore processors 802, coupled to a non-transitory computer readablestorage medium 820 via an input/output (I/O) interface 810. The aerialvehicle control system 800 may also include an electronic speed controlor propulsion controller 804, a power controller/supply module 806and/or a navigation system 808. The aerial vehicle control system 800further includes a propeller blade pitch controller 812, a networkinterface 816, and one or more input/output devices 818.

In various implementations, the aerial vehicle control system 800 may bea uniprocessor system including one processor 802, or a multiprocessorsystem including several processors 802 (e.g., two, four, eight, oranother suitable number). The processor(s) 802 may be any suitableprocessor capable of executing instructions. For example, in variousimplementations, the processor(s) 802 may be general-purpose or embeddedprocessors implementing any of a variety of instruction setarchitectures (ISAs), such as the x86, PowerPC, SPARC, or MIPS ISAs, orany other suitable ISA. In multiprocessor systems, each processor(s) 802may commonly, but not necessarily, implement the same ISA.

The non-transitory computer readable storage medium 820 may beconfigured to store executable instructions, data, propeller blade dataor characteristics, blade pitch data or characteristics, propeller bladepitch adjustment apparatus data or characteristics, data orcharacteristics associated with the aerial vehicle or any other systemor machine utilizing the propeller blade pitch adjustment apparatuses,and/or other data items accessible by the processor(s) 802. In variousimplementations, the non-transitory computer readable storage medium 820may be implemented using any suitable memory technology, such as staticrandom access memory (SRAM), synchronous dynamic RAM (SDRAM),nonvolatile/Flash-type memory, or any other type of memory. In theillustrated implementation, program instructions and data implementingdesired functions, such as those described above, are shown storedwithin the non-transitory computer readable storage medium 820 asprogram instructions 822, data storage 824 and propeller blade, bladepitch, and operational data 826, respectively. In other implementations,program instructions, data and/or operational data may be received, sentor stored upon different types of computer-accessible media, such asnon-transitory media, or on similar media separate from thenon-transitory computer readable storage medium 820 or the aerialvehicle control system 800. Propeller blade pitch adjustment apparatusdata or characteristics may include data related to motor shafts 108,pitch adjustment shafts 122, blade gears 217, pitch adjustment gears215, first sun gears 315, first planet gears 325, first planetary gearcarriers 123, ring gears 330, second planet gears 425, second planetarygear carriers 124, second sun gears 415, control shafts 610, 710,control members 615, 715, pitch adjustment spools 620, 720, tensioncables 622, torsion springs 625, racks 717, and/or any other componentsof the apparatuses 100-700 described herein.

Generally speaking, a non-transitory, computer readable storage mediummay include storage media or memory media such as magnetic or opticalmedia, e.g., disk or CD/DVD-ROM, coupled to the aerial vehicle controlsystem 800 via the I/O interface 810. Program instructions and datastored via a non-transitory computer readable medium may be transmittedby transmission media or signals, such as electrical, electromagnetic,or digital signals, which may be conveyed via a communication mediumsuch as a network and/or a wireless link, such as may be implemented viathe network interface 816.

In one implementation, the I/O interface 810 may be configured tocoordinate I/O traffic between the processor(s) 802, the non-transitorycomputer readable storage medium 820, and any peripheral devices, thenetwork interface 816 or other peripheral interfaces, such asinput/output devices 818. In some implementations, the I/O interface 810may perform any necessary protocol, timing or other data transformationsto convert data signals from one component (e.g., non-transitorycomputer readable storage medium 820) into a format suitable for use byanother component (e.g., processor(s) 802). In some implementations, theI/O interface 810 may include support for devices attached throughvarious types of peripheral buses, such as a variant of the PeripheralComponent Interconnect (PCI) bus standard or the Universal Serial Bus(USB) standard, for example. In some implementations, the function ofthe I/O interface 810 may be split into two or more separate components,such as a north bridge and a south bridge, for example. Also, in someimplementations, some or all of the functionality of the I/O interface810, such as an interface to the non-transitory computer readablestorage medium 820, may be incorporated directly into the processor(s)802.

The electronic speed control or propulsion controller 804 communicateswith the navigation system 808 and adjusts the operationalcharacteristics of each propulsion mechanism to guide the aerial vehiclealong a determined flight path and/or to perform other navigationalmaneuvers. The navigation system 808 may include a GPS or other similarsystem than can be used to navigate the aerial vehicle to and/or from alocation.

The aerial vehicle control system 800 may also include a propeller bladepitch controller 812. The propeller blade pitch controller 812communicates with components of the aerial vehicle, as discussed above,and controls the actuation of the second planetary gear carrier 124 andpitch adjustment shaft 122, control shaft 610, and/or control shaft 710to adjust pitches of propeller blades. For example, an aerial vehiclecontrol system 800 may operate a motor in a first rotational directionto generate thrust with a corresponding propeller, and if a thrustreversal is desired, the propeller blade pitch controller 812 mayactuate the second planetary gear carrier 124 and pitch adjustment shaft122, control shaft 610, and/or control shaft 710 to adjust pitches ofthe one or more propeller blades, e.g., rotate the blades byapproximately 180 degrees, and the aerial vehicle control system 800 mayoperate the motor in a second rotational direction opposite from thefirst rotational direction.

The network interface 816 may be configured to allow data to beexchanged between the aerial vehicle control system 800, other devicesattached to a network, such as other computer systems, aerial vehiclecontrol systems of other aerial vehicles, and/or an aerial vehiclemanagement system. For example, the network interface 816 may enablewireless communication between numerous aerial vehicles. In variousimplementations, the network interface 816 may support communication viawireless general data networks, such as a Wi-Fi network. For example,the network interface 816 may support communication viatelecommunications networks such as cellular communication networks,satellite networks, and the like.

Input/output devices 818 may, in some implementations, include one ormore displays, image capture devices, imaging sensors, thermal sensors,infrared sensors, time of flight sensors, accelerometers, pressuresensors, weather sensors, etc. Multiple input/output devices 818 may bepresent and controlled by the aerial vehicle control system 800. One ormore of these sensors may be utilized to determine an aerial vehicleoperation, a flight condition, a location, and/or a time at which achange of pitch is desired for one or more propellers of the aerialvehicle.

As shown in FIG. 8, the memory may include program instructions 820which may be configured to implement the example processes and/orsub-processes described above. The data storage 824 and propeller blade,blade pitch, and operational data 826 may include various data storesfor maintaining data items that may be provided for controlling theactuation of the various propeller blade pitch adjustment apparatusesdescribed herein to adjust pitches of propeller blades.

In various implementations, the parameter values and other dataillustrated herein as being included in one or more data stores may becombined with other information not described or may be partitioneddifferently into more, fewer, or different data structures. In someimplementations, data stores may be physically located in one memory ormay be distributed among two or more memories.

Each process described herein may be implemented by the architecturesdescribed herein or by other architectures. The processes areillustrated as a collection of blocks in a logical flow. Some of theblocks represent operations that can be implemented in hardware,software, or a combination thereof. In the context of software, theblocks represent computer-executable instructions stored on one or morecomputer readable media that, when executed by one or more processors,perform the recited operations. Generally, computer-executableinstructions include routines, programs, objects, components, datastructures, and the like that perform particular functions or implementparticular abstract data types.

The computer readable media may include non-transitory computer readablestorage media, which may include hard drives, floppy diskettes, opticaldisks, CD-ROMs, DVDs, read-only memories (ROMs), random access memories(RAMs), EPROMs, EEPROMs, flash memory, magnetic or optical cards,solid-state memory devices, or other types of storage media suitable forstoring electronic instructions. In addition, in some implementations,the computer readable media may include a transitory computer readablesignal (in compressed or uncompressed form). Examples of computerreadable signals, whether modulated using a carrier or not, include, butare not limited to, signals that a computer system hosting or running acomputer program can be configured to access, including signalsdownloaded through the Internet or other networks. Finally, the order inwhich the operations are described is not intended to be construed as alimitation, and any number of the described operations can be combinedin any order and/or in parallel to implement the process. Additionally,one or more of the operations may be considered optional and/or notutilized with other operations.

Those skilled in the art will appreciate that the aerial vehicle controlsystem 800 is merely illustrative and is not intended to limit the scopeof the present disclosure. In particular, the computing system anddevices may include any combination of hardware or software that canperform the indicated functions, including computers, network devices,internet appliances, PDAs, wireless phones, pagers, etc. The aerialvehicle control system 800 may also be connected to other devices thatare not illustrated, or instead may operate as a stand-alone system. Inaddition, the functionality provided by the illustrated components may,in some implementations, be combined in fewer components or distributedin additional components. Similarly, in some implementations, thefunctionality of some of the illustrated components may not be providedand/or other additional functionality may be available.

Those skilled in the art will also appreciate that, while various itemsare illustrated as being stored in memory or storage while being used,these items or portions of them may be transferred between memory andother storage devices for purposes of memory management and dataintegrity. Alternatively, in other implementations, some or all of thesoftware components may execute in memory on another device andcommunicate with the illustrated aerial vehicle control system 800. Someor all of the system components or data structures may also be stored(e.g., as instructions or structured data) on a non-transitory,computer-accessible medium or a portable article to be read by anappropriate drive, various examples of which are described above. Insome implementations, instructions stored on a computer-accessiblemedium separate from the aerial vehicle control system 800 may betransmitted to the aerial vehicle control system 800 via transmissionmedia or signals, such as electrical, electromagnetic, or digitalsignals, conveyed via a communication medium, such as a network and/or awireless link. Various implementations may further include receiving,sending or storing instructions and/or data implemented in accordancewith the foregoing description upon a computer-accessible medium.Accordingly, the techniques described herein may be practiced with otheraerial vehicle control system configurations.

Those skilled in the art will appreciate that, in some implementations,the functionality provided by the processes and systems discussed abovemay be provided in alternative ways, such as being split among moresoftware modules or routines or consolidated into fewer modules orroutines. Similarly, in some implementations, illustrated processes andsystems may provide more or less functionality than is described, suchas when other illustrated processes instead lack or include suchfunctionality respectively, or when the amount of functionality that isprovided is altered. In addition, while various operations may beillustrated as being performed in a particular manner (e.g., in serialor in parallel) and/or in a particular order, those skilled in the artwill appreciate that, in other implementations, the operations may beperformed in other orders and in other manners. Those skilled in the artwill also appreciate that the data structures discussed above may bestructured in different manners, such as by having a single datastructure split into multiple data structures or by having multiple datastructures consolidated into a single data structure. Similarly, in someimplementations, illustrated data structures may store more or lessinformation than is described, such as when other illustrated datastructures instead lack or include such information respectively, orwhen the amount or types of information that is stored is altered. Thevarious processes and systems as illustrated in the figures anddescribed herein represent example implementations. The processes andsystems may be implemented in software, hardware, or a combinationthereof in other implementations. Similarly, the order of any processmay be changed and various elements may be added, reordered, combined,omitted, modified, etc., in other implementations.

From the foregoing, it will be appreciated that, although specificimplementations have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of the appended claims and the features recited therein. Inaddition, while certain aspects are presented below in certain claimforms, the inventors contemplate the various aspects in any availableclaim form. For example, while only some aspects may currently berecited as being embodied in a computer readable storage medium, otheraspects may likewise be so embodied. Various modifications and changesmay be made as would be obvious to a person skilled in the art havingthe benefit of this disclosure. It is intended to embrace all suchmodifications and changes and, accordingly, the above description is tobe regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A propeller blade pitch adjustment apparatuscomprising: a propeller hub coupled to a first end of a hollow motorshaft and rotated by the hollow motor shaft, the propeller hubcomprising: a plurality of propeller blade shafts, each propeller bladeshaft coupled to a respective propeller blade that extends outside ofthe propeller hub, and coupled to a respective bevel gear inside thepropeller hub; and a pitch adjustment bevel gear that is in operativeengagement with respective bevel gears coupled to the plurality ofpropeller blade shafts, the pitch adjustment bevel gear coupled to afirst end of a pitch adjustment shaft that extends within the hollowmotor shaft; and a compound gearbox comprising a first stage gearbox anda second stage gearbox, the first stage gearbox comprising: a first sungear coupled to a second end of the hollow motor shaft and rotated bythe hollow motor shaft; a plurality of first planet gears that is inoperative engagement with the first sun gear and carried by a firstplanetary gear carrier, the first planetary gear carrier beingrotationally fixed relative to a stator of a motor that rotates thehollow motor shaft; and a ring gear that is in operative engagement withthe plurality of first planet gears; and the second stage gearboxcomprising: a plurality of second planet gears that is in operativeengagement with the ring gear and carried by a second planetary gearcarrier, the second planetary gear carrier being rotatable relative tothe first planetary gear carrier; and a second sun gear that is coupledto a second end of the pitch adjustment shaft and being in operativeengagement with the plurality of second planet gears; wherein a rotationof the second planetary gear carrier relative to the first planetarygear carrier causes to rotate the pitch adjustment shaft and the pitchadjustment bevel gear to adjust respective pitches of the plurality ofpropeller blades; wherein the first sun gear, the first planetary gearcarrier, the ring gear, the second planetary gear carrier, and thesecond sun gear are coaxially aligned.
 2. The propeller blade pitchadjustment apparatus of claim 1, wherein the propeller hub and thecompound gearbox are positioned on opposite sides of the motor.
 3. Thepropeller blade pitch adjustment apparatus of claim 1, wherein thehollow motor shaft is coupled to and rotated by a rotor of the motor. 4.The propeller blade pitch adjustment apparatus of claim 1, wherein thefirst planetary gear carrier of the first stage gearbox of the compoundgearbox is coupled to the stator of the motor.
 5. An apparatuscomprising: a propeller hub coupled to a first end of a motor shaft, thepropeller hub comprising: a propeller blade shaft that is coupled to apropeller blade, and coupled to a blade gear within the propeller hub;and a pitch adjustment gear that is in operative engagement with theblade gear coupled to the propeller blade shaft, the pitch adjustmentgear coupled to a first end of a pitch adjustment shaft that extendscoaxially with the motor shaft; and a gearbox comprising a firstplanetary stage and a second planetary stage, the first planetary stagecomprising: a first sun gear coupled to a second end of the motor shaft;a plurality of first planet gears that is in operative engagement withthe first sun gear and carried by a first planetary gear carrier, thefirst planetary gear carrier being rotationally fixed relative to astator of a motor that rotates the motor shaft, and the first planetarygear carrier being coaxially aligned with the first sun gear; and a ringgear that is in operative engagement with the plurality of first planetgears; and the second planetary stage comprising: a plurality of secondplanet gears that is in operative engagement with the ring gear andcarried by a second planetary gear carrier, the second planetary gearcarrier being rotatable relative to the first planetary gear carrier;and a second sun gear that is coupled to a second end of the pitchadjustment shaft and being in operative engagement with the plurality ofsecond planet gears, the second sun gear being coaxially aligned withthe second planetary gear carrier.
 6. The apparatus of claim 5, whereinthe propeller hub further comprises: a plurality of propeller bladeshafts, each propeller blade shaft coupled to a respective propellerblade that extends outside of the propeller hub, and coupled to arespective blade gear inside the propeller hub; and wherein the pitchadjustment gear is in operative engagement with respective blade gearsthat are coupled to the plurality of propeller blade shafts.
 7. Theapparatus of claim 5, wherein the blade gear is one of a straight bevelgear and a spiral bevel gear, and the pitch adjustment gear is one of astraight bevel gear and a spiral bevel gear.
 8. The apparatus of claim5, wherein the motor shaft is hollow and the pitch adjustment shaftextends within the hollow motor shaft, or the pitch adjustment shaft ishollow and the motor shaft extends within the hollow pitch adjustmentshaft.
 9. The apparatus of claim 5, wherein the motor shaft is rotatedby a rotor of the motor, in response to which the propeller hub coupledto the first end of the motor shaft and the first sun gear coupled tothe second end of the motor shaft rotate.
 10. The apparatus of claim 9,wherein each of the plurality of first planet gears rotates on therotationally fixed first planetary gear carrier, and the ring gearrotates around the first sun gear and the plurality of first planetgears in response to rotation of the first sun gear.
 11. The apparatusof claim 10, wherein the plurality of second planet gears rotates on thesecond planetary gear carrier, and the second sun gear rotates inresponse to rotation of the ring gear.
 12. The apparatus of claim 11,wherein the motor shaft and the pitch adjustment shaft rotate in a samedirection at a same rotational speed, in response to the secondplanetary gear carrier being rotationally held in place relative to thefirst planetary gear carrier.
 13. The apparatus of claim 5, furthercomprising: an actuator configured to rotate the second planetary gearcarrier.
 14. The apparatus of claim 13, wherein the actuator comprisesat least one of a servo actuator, a geared actuator, a rotary actuator,a rack and pinion actuator, or a screw actuator.
 15. The apparatus ofclaim 13, wherein the pitch adjustment shaft rotates relative to themotor shaft to adjust a pitch of the propeller blade in response torotation of the second planetary gear carrier relative to the firstplanetary gear carrier.
 16. A method of adjusting a pitch of a propellerblade comprising: adjusting an angular position of a second planetarygear carrier relative to a first planetary gear carrier, the firstplanetary gear carrier being rotationally fixed relative to a stator ofa motor that rotates a motor shaft, the first planetary gear carriercarrying a plurality of first planet gears in operative engagement witha first sun gear and a ring gear, and the second planetary gear carrierbeing rotatable and carrying a plurality of second planet gears inoperative engagement with the ring gear and a second sun gear; whereinthe first sun gear is coupled to the motor shaft that rotates apropeller hub having a propeller blade shaft and an associated propellerblade, and the second sun gear is coupled to a pitch adjustment shaftthat is in operative engagement with the propeller blade shaft withinthe propeller hub to adjust a pitch of the associated propeller blade;wherein the propeller blade shaft is coupled to a blade gear within thepropeller hub, the pitch adjustment shaft is coupled to a pitchadjustment gear within the propeller hub, and the blade gear and thepitch adjustment gear are in operative engagement to adjust the pitch ofthe associated propeller blade; wherein the pitch adjustment shaftextends coaxially with the motor shaft; and wherein the first planetarygear carrier, the first sun gear, the ring gear, the second planetarygear carrier, and the second sun gear are coaxially aligned.
 17. Themethod of claim 16, wherein the adjusting is caused by an actuator thatrotates the second planetary gear carrier relative to the firstplanetary gear carrier.
 18. The method of claim 16, further comprising:causing rotation of the motor shaft via a rotor of the motor; andmaintaining a rotational position of the first planetary gear carrierrelative to the stator of the motor.
 19. The method of claim 16, whereinthe propeller hub includes a plurality of propeller blade shafts andassociated propeller blades, each of the plurality of propeller bladeshafts being in operative engagement with the pitch adjustment shaft toadjust respective pitches of the associated propeller blades.